Typically, a single will receive up to six weeks' airplay before it's released, in an effort to get the song to chart high in its first week on sale. That, however, does not mean fans can't download it – only that they can't pay for it. Chances are anyone swiftly searching on Google for a track they heard on the radio, but which is not yet commercially released, will find a site where they can download it illegally – or even scrape it off YouTube.

David Joseph, the chief executive of Universal Music, was the first major label executive to champion the move to close the gap. He was joined by Sony, who had witnessed their X Factor acts score high sales when songs featured on the talent show became instantly available for sale online.

Yet I've noticed there have been more and more exceptions to the rule in the past few months. Despite Maverick Sabre's single being all over Radio 1 and Radio 2 for weeks, it was only released last week by Universal. So what happened? The answer lies in how chart positions affect what radio stations put on their playlists.

George Ergatoudis, head of music for Radio 1 and 1Xtra, says he's noticed that Universal has "taken the foot off the gas a bit". He acknowledges Radio 1's purpose as a public service is to nurture and develop talent, but adds that they have to strike a balance between chart acts and unknowns in their playlists so that people will continue listening to the station. Yet he says he also realises the songs that end up meaning the most to most people don't grab them on the first few listens. As Radio 1 usually plays their top tracks 25-26 times a week (Capital, he says, plays top tracks 80-100 times a week), but usually start out by playing songs less than that. This means it could take three to four weeks before a listener has heard a track a few times. That's why sales in singles will usually peak after a month on the radio.

Ergatoudis says "on air, on sale" has not changed Radio 1's behaviour, as they've always taken risks. "Take Mumford & Sons," he explains. "When we researched the first single, people didn't seem to get it. It wasn't until the third single that the audience got it. It takes faith. We lead and others follow.

"We were optimistic about the move, though we realised it would involve some initial pain. Capital Radio took the Saturdays' Notorious off their playlist just because sales reduced a bit after a few weeks, but we stuck with it – and it turns out we were right."

Some may say the "on air, on sale" move was doomed from the start, as many labels refused to play ball. It could only really work if everyone was on board, as otherwise it would create an uneven playing field. Notably Ministry of Sound, which would not go along with the scheme, had a long lead-up to the release of Example's Changed the Way You Kiss Me and were rewarded with a No 1 hit in the charts in its first week of release.

Meanwhile, Universal artists the Saturdays and Nicola Roberts watched as their singles (Notorious and Beat of My Drum respectively) were taken off radio playlists after entering the charts at a low position. One label claimed that Global Radio – the biggest commercial radio conglomerate in the UK, with a roster of stations including Capital, Heart and Xfm – refuses to playlist songs that go on sale at the same time as they are serviced to radio (Global Radio declined to comment on this allegation).

All the record labels and radio pluggers I've spoken to agree they'd be much worse off without the BBC, which can afford to broadcast music that wouldn't fit into the narrow requirements of commercial radio stations. Maybe the Beeb is the reason radio is even more influential when it comes to record sales in the UK than in the US. But is BBC airplay enough for a record to succeed? Those labels that didn't sign up to "day and date" argue it should be decided on a case-by-case basis. Stars such as Kanye West and David Guetta benefit more from closing the gap, as their records tend to leak on the net as soon as they're mastered – often even before they're even finished – due to public demand. New and unknown artists, however, need the six-week build-up before the release to create awareness.

The FAC and MMF says this compromise isn't good enough. "As an industry, we're either in favour of a world where artists, labels and managers hold back releases to manipulate the charts, or we're in favour of a world where licensed download services are the first port of call for new music. Which is it?" they ask.

Yet, as research shows that radio is the chief factor in driving record sales in the UK – and that most record buyers only buy music on the iTunes front-page top 10 – some artists and their managers are now telling labels to revert to the old ways, according to sources. Could it be that they agree to "day and date" in principle, but when it comes down to something as important as their own individual success, it's every artist for themselves?